Why do i have '?' and 'M' in the class folder Xcode 4?

Do not really understand how to ask this question so i added a picture below. My question is why I have '?' and and 'M' to the right?

Also, what should i do with it?

I am currently doing tutorial in 开发者_运维知识库Cocos2D.

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See this page (the table under Section Keep Track of Your Files’ SCM Status ).

Badge   SCM Status

M        Locally modified

?        Not under source control

and there's a few more.